The invention relates, in general, to electrode structures deployable into interior regions of the body, and, in particular, to electrode structures deployable into the heart for diagnosis and treatment of cardiac conditions.
It is known that the effective treatment of cardiac arrhythmias requires creating tissue lesions having a diversity of different geometries and characteristics, depending upon the particular physiology of the arrhythmia to be treated. This recognition is discussed in U.S. patent application Ser. No. 08/631,356, filed Apr. 12, 1996, and Provisional Application Serial Nos. 60/010,223, 60/010,225, and 60/010,354, which were filed on Jan. 19, 1996. These applications are fully incorporated herein by reference for all they disclose and describe.
As discussed therein, one proposed solution to the creation of diverse lesion characteristics is to use different forms of ablation energy, e.g., microwave, laser, ultrasound, and chemical ablation. However, these technologies are largely unproven for this purpose.
The use of active cooling in association with the transmission of DC or radio frequency (xe2x80x9cRFxe2x80x9d) ablation energy is known to force the electrode-tissue interface to lower temperature values. As a result, the hottest tissue temperature region is shifted deeper into the tissue, which, in turn, shifts the boundary of the tissue rendered nonviable by ablation deeper into the tissue. An electrode that is actively cooled can be used to transmit more ablation energy into the tissue, compared to the same electrode that is not actively cooled. However, control of active cooling is required to keep maximum tissue temperatures safely below about 100xc2x0 C., at which tissue desiccation or tissue boiling is known to occur.
The treatment of some cardiac arrhythmias requires creating significantly large and deep lesions or lesions having relatively large surface areas with shallow depths. A proposed solution to the creation of these larger lesions is the use of substantially larger electrodes than those commercially available. However, larger electrodes themselves pose problems of size and maneuverability, which weigh against safe and easy introduction of large electrodes through a vein or an artery, and into the heart.
In an effort to solve the problems of maneuverability and safe introduction, collapsible ablation structures have been developed. These structures are manipulated to a collapsed position during introduction and maneuvering, and to an expanded position during ablation of the desired heart tissue. Numerous examples of such structures are shown and described in the above-referenced application. A number of the collapsible ablation structures disclosed therein include a balloon with a microporous membrane or coating made of regenerated cellulose that is filled with a hypertonic solution such as saline. In particular, the hypertonic solution acts as both a current carrying means and an inflation medium for expanding the balloon.
A balloon coating made of regenerated cellulose is desirable because it is an ion-permeable material, allowing the ionic transfer of electrical energy from an electrode disposed in the balloon interior into a patient""s bloodstream and/or body tissue, while preventing macromolecules, such as blood proteins, from passing into the balloon.
The regenerated cellulose coating also acts as a biocompatible barrier between the catheter components and the body tissue, thereby allowing the components to be made from less expensive materials that may be somewhat toxic, e.g., silver or copper. The regenerated cellulose acts as a biocompatible barrier because it increases the diffusional distance to the body tissue and reduces the percentage of metallic surface directly and indirectly exposed to the tissue.
A problem with regenerated cellulose is that it is not known to be formable or moldable into a three-dimensional body structure such as that required for proper lesion creation. Also, regenerated cellulose is not known to be formable with operative elements, e.g., temperatures sensors, embedded therein, or formable so as to have a smooth exterior, as required for a tissue-contacting electrode body structure.
It would be desirable, therefore, to provide a method for manufacturing a three-dimensional electrode body structure made of regenerated cellulose.
During minimally-invasive diagnostic and therapeutic cardiac procedures such as endocardial mapping and ablating, the heart muscles continuously expand and contract with the beating of the heart, i.e., heart diastole and heart systole. When deployed in this environment, an catheter electrode assembly is subject to alternate cycles of contraction and expansion. The surface pressure of the electrode assembly against the moving endocardium can continuously vary, complicating the task of performing the diagnostic and/or therapeutic procedure desired.
A need therefore exists for a means for continuously urging the electrode assembly against the endocardium and for maintaining a constant surface pressure, despite contraction and expansion of the heart.
A need also exists for a means of evaluating the sufficiency of the surface contact of the electrode assembly with the endocardium so the operating physician will know ahead of time what the potential for success is for the diagnostic or therapeutic procedure to be performed on the heart.
According to one aspect of the invention, methods of manufacturing cellulosic structures, such as, e.g., for use in expandable-collapsible electrode assemblies for diagnostic and/or therapeutic electrophysiology devices, are disclosed. One such preferred method includes providing a mandrel having a head portion and a neck portion, the head portion having an outer circumference greater than the neck portion, dipping the mandrel into a cellulosic substance, curing the cellulosic substance, and separating the mandrel from the cured cellulosic substance.
According to a separate aspect of the invention, an electrode assembly is provided, which includes an expandable-collapsible body and a biasing device adapted to resiliently urge a distal portion of the body against adjacent body tissue.
According to yet another aspect of the invention, an electrode assembly is provided, which includes a regenerated cellulosic body substantially enclosing an interior area, a center support disposed in the interior area, and an electrode disposed on the center support.
Other, more particular features and advantages of the inventions are set forth in the following detailed description and drawings.
The drawings illustrate both the design and utility of preferred embodiments of the present invention, in which similar elements are referred to by common reference numbers, wherein:
FIG. 1A is a perspective view of an embodiment of a system for ablating heart tissue and illustrates an exemplary catheter assembly, including an expandable electrode structure, for ablating heart tissue;
FIG. 1B is a perspective view of a lumen guide assembly of the catheter assembly illustrated in FIG. 1A;
FIG. 1C is a top view of an embodiment of a pressure-relief mechanism for the expandable electrode structure;
FIG. 2 is an enlarged cross-sectional view of an electrode structure constructed in accordance with an embodiment of the invention;
FIG. 3 is a partial, cut-away side view of a shaft and a receiver of the electrode structure illustrated in FIG. 2, and illustrates an embodiment of a mechanism for determining the displacement of the shaft;
FIG. 4 is a partial, cut-away side view of a shaft and a receiver of the electrode structure illustrated in FIG. 2, and illustrates an alternative embodiment of a mechanism for determining the displacement of the shaft;
FIG. 5 is an enlarged cross-sectional view of an electrode structure constructed in accordance with another embodiment of the invention;
FIGS. 6A and 6B are an enlarged side elevational view and a top plan view, respectively, of an electrode structure constructed in accordance with a further preferred embodiment of the invention;
FIG. 7 is an enlarged cross-sectional view of an electrode structure constructed in accordance with an additional embodiment of the invention;
FIGS. 8A and 8B are an enlarged longitudinal cross-sectional view and an enlarged lateral cross-sectional view, respectively, of an electrode structure constructed in accordance with a further preferred embodiment of the invention;
FIG. 9A is an enlarged, partially cut-away side elevational view of an electrode structure constructed in accordance with yet another embodiment of the invention;
FIG. 9B is a top plan view of an embodiment of a rib support assembly illustrated in FIG. 9A;
FIGS. 10A-10C are side elevational views of exemplary mandrels that may be used in manufacturing the electrode structure of the present invention;
FIGS. 11A and 11B are a top plan view and a cross-sectional view, respectively, of a balloon support illustrated in FIG. 8A, and illustrate a step in assembling the electrode structure illustrated in FIG. 8A;
FIGS. 12A and 12B are a top plan view and a cross-sectional view, respectively, of the balloon support and electrode illustrated in FIG. 8A, and illustrate another step in assembling the electrode structure illustrated in FIG. 8A;
FIGS. 13A and 13B are a top plan view and a cross-sectional view, respectively, of the balloon support, electrode, and lumens illustrated in FIG. 8A, and illustrate an additional step in assembling the electrode structure illustrated in FIG. 8A;
FIG. 14 is a cross-sectional view of the balloon support, electrode, lumens, and body of the electrode structure illustrated in FIG. 8A, and illustrates a further step in assembling the electrode structure illustrated in FIG. 8A;
FIG. 15 is a cross-sectional view of the balloon support, electrode, lumens, body, and distal portion of the steering wire assembly of the electrode structure illustrated in FIG. 8A, and illustrates an additional step in assembling the electrode structure illustrated in FIG. 8A; and
FIG. 16 is a cross-sectional view of the electrode structure illustrated in FIG. 8A and a distal portion of the catheter, and illustrates a still further step in assembling the electrode structure illustrated in FIG. 8A.